1. Field of the Invention
The invention relates to a system for fastening a rail to a solid foundation, on which a support section is arranged, which supports the rail to be fastened in the finally installed state.
The invention also relates to a method for renovating a rail-fastening point, at which the rail by means of a spring element tensioned by a clamping element and acting on its rail foot, is supported in an elastic manner on a support section of a sleeper in a solid material at risk from abrasion.
2. Description of Related Art
A large number of rail fastening systems of the abovementioned type which can be renovated with a method according to the invention are known. A typical example of such a fastening system which is widely used in practice and has been tried and tested is described in more detail in the installation instructions for the “Schienenbefestigungssystem W14” (W14 rail fastening system), which can be downloaded from http://vossloh-rail-systems.de.
The W14 rail fastening system is based on a concrete sleeper, in which a level, and, seen in plan view, rectangular support section for the foot of respective rail to be fastened is formed. As an alternative to a sleeper, concrete plates are also used for supporting the rails on the respective foundation and which have a corresponding design. The following explanations apply in this respect equally to all such plates or sleepers.
Seen in the longitudinal direction of the rail to be fastened, the respective support section extends across the entire sleeper, while its width measured transverse to the longitudinal extension of the rail is greater than the width of the rail foot, but smaller than the total width of the sleeper. On its narrow sides oriented parallel to the longitudinal extension of the rail the support section is delimited by in each case a depression likewise extending parallel to the longitudinal extension of the rail to be fastened over the sleeper, and having a substantially V-shaped cross section. In addition, in each of the areas of the support section present either side of the section occupied by the rail foot in the installed state a seat is formed for a dowel or similar, into which a tensioning screw can be screwed.
For fastening the rail on each of the areas of the support section not occupied by the rail foot a so-called “angled guide plate” is positioned. These angled guide plates, which for weight reasons and for the purposes of improving the elastic behaviour and the electrical resistance, are normally made from a high-strength plastic material, have a central section, on the lower face of which a support surface is formed, with which the angled guide plates sit on the support section. With the angled guide plate used for the W14 system, on the central section a support section is also formed, which starting from the support surface on the lower face of the angled guide plate extends downwards and the shape of which is matched to the shape of the depressions of the sleeper delimiting the support section. In the installed state each of the angled guide plates accordingly has a form-fit between its support section and the respectively associated depression. With their contact surface opposite the support section the angled guide plates on the other hand rest laterally on the foot of the rail to be fastened. Lateral forces which are transferred from the rail to the angled guide plates can thus be absorbed by the angled guide plates and introduced into the sleeper. Here the angled guide plates are supported by the lateral surface of the respective depression turned away from the rail.
In order to secure the rail from lifting in the known rail fastening systems normally spring elements are used, which in the installed state exert a resilient elastic retention force on the rail foot. The spring elements used in the W14 rail fastening system and similar systems, and also known as “tensioning clamps” have a W-shaped design and with their mid-section are braced against the angled guide plate. To this end in the angled guide plate a through opening is formed, via which the tensioning screw used to tension the respective tensioning clamp can be screwed into the respective dowel embedded in the sleeper.
Upon completion of installation the tensioning clamp which in this state is braced against the sleeper rests with its supporting arms extending from the mid-section on the foot of the rail to be fastened. Thus the supporting arms transmit spring forces to the rail foot, which on the one hand are strong enough to prevent excessive lifting of the rail, but on the other are elastic enough for the rail to be able to move sufficiently up and down in the vertical direction when passed over by a rail vehicle. In this way the rail is held secure but can nevertheless compensate for its deformations caused by the weight and movement of the rail vehicle.
In order to ensure the required flexibility of a rail fastening point designed in the abovementioned way, normally between the rail foot and the support section an intermediate layer in elastically flexible material is arranged.
Practical experience shows that under unfavourable installation or operational conditions considerable abrasive wear of the respective sleeper or plate occurs in the area of its support section. The wear manifests itself as irregular material removal. This can become so extreme that between the rail foot and the support section a air gap is permanently present, as a result of which secure support for the rail in the respective fastening point is no longer guaranteed and any inclination provided for the rail is permanently altered in an inadmissible manner.
It is known that an air gap which may be present between a sleeper and a ballast bed or a concrete plate, on which the sleeper stands, because of unavoidable structural inaccuracies, can be closed up by the injection of a filler (DE 19929283 A1, JP 2002/242103 A). Applying this known method to the renovation of rail fastening points at which between the support section of the sleeper and the rail foot as a result of abrasive wear an air gap has formed, proves to be problematical, however, since the forces of pressure applied to the respective fastening point when it is being passed over are so high that the filler that has been injected is not resistant for a sufficiently long period of use. It also proves difficult to apply the injection mass in such a way that any elastic intermediate layer present can continue to perform its function.
Against this background the problem for the invention was to provide a system and a method allowing a fastening point for a rail to be easily and economically renovated in such a way that a permanently reliable functioning of the renovated fastening is then ensured again while the worn support section remains.